The Collaborative International Dictionary of English v.0.48:

Interstice \In*ter"stice\ (?; 277), n.; pl. Interstices. [L.
   interstitium a pause, interval; inter between + sistere to
   set, fr. stare to stand: cf. F. interstice. See Stand.]
   [1913 Webster]
   1. That which intervenes between one thing and another;
      especially, a space between things closely set, or between
      the parts which compose a body; a narrow chink; a crack; a
      crevice; a hole; an interval; as, the interstices of a
      wall.
      [1913 Webster]

   2. An interval of time; specifically (R. C. Ch.), in the
      plural, the intervals which the canon law requires between
      the reception of the various degrees of orders.
      [1913 Webster]

            Nonobservance of the interstices . . . is a sin.
                                                  --Addis &
                                                  Arnold.
      [1913 Webster]

WordNet (r) 3.0 (2006):

interstice
    n 1: a small structural space between tissues or parts of an
         organ; "the interstices of a network"
    2: small opening between things

Moby Thesaurus II by Grady Ward, 1.0:

26 Moby Thesaurus words for "interstice":
   caesura, clearance, discontinuity, distance between, double space,
   em space, en space, freeboard, hair space, half space, hiatus,
   interim, intermediate space, interruption, interspace, interval,
   jump, lacuna, leap, leeway, margin, room, single space, space,
   space between, time interval